Technical Abstract:
Candidatus Liberibacter asiaticus is one of the three known bacterial Candidatus species causing citrus Huanglongbing (HLB) or yellow shoot disease. HLB is highly destructive in citrus cultivation and is currently known to presence in Asia, Africa, South and North America. Pathogen detection plays a key role in HLB control. Because of the uncultureable status, C. L. species is currently defined by the characteristic of 16S rDNA sequence. In this study, HLB was first recognized by symptomatology. C. L. asiaticus was detected by PCR from DNA extracted from diseased citrus tissue. We experienced that low bacterial titer and possible inhibitors from plant tissue were the challenge for quick and accurate PCR detection. We overcome this problem by a PCR using the specific primer set OI1 and OI2c nested with a primer set general to bacterial 16S rDNA. This nested PCR format was also performed on a SYBR green based real-time PCR with comparable detection sensitivity and accuracy, but eliminated the post-PCR agarose gel electrophoresis process.